Nearly 30 years after launch, the two Voyager spacecraft are still operational and returning useful data. In their early years they produced some of the first close up images of the large outer planets. Now as the two vehicles, flying in slightly different directions, near the edge of the solar system, they are providing clues on the shape of heliosphere, and quite possibly, the direction of the solar system through local space.

Nearly 30 years after launch, the two Voyager spacecraft are still operational and returning useful data. In their early years they produced some of the first close up images of the large outer planets. Now as the two vehicles, flying in slightly different directions, near the edge of the solar system, they are providing clues on the shape of heliosphere, and quite possibly, the direction of the solar system through local space.

The heliosphere, generated by the Sun, is sort of the cocoon in which the solar system rides. It has been suspected for several years that it is not spherical but more egg shaped. Voyager 1 recently reached one edge and it is estimated it will pass into interstellar space at about 12.4 billion miles from the Sun. It was recently announced that Voyager 2 has reached its more southerly edge, sooner than expected. It is now believed it will reach interstellar space at about 10.5 billion miles. This reveals that the heliosphere is not a sphere after all, but is more of a comet shape.

According to Cal Tech's Ed Stone, the former director of NASA's Jet Propulsion Laboratory and a Voyager chief scientist, the shape of the bubble is determined by what is pressing on the solar system from the outside, meaning the shape and force of interstellar gases. That is one explanation. Another put forth by Walter Cruttenden of the Binary Research Institute is that local gases are fairly uniform and the shape derives from the trajectory of the solar system through local space — possibly in its orbit around a companion star. While this latter explanation is far more speculative, it is not unlikely that local interstellar gases are relatively homogeneous and therefore the shape of the heliosphere may be at least partially due to motion of the solar system.

Voyager 1 and 2 are expected to remain active for several more decades. In that time we should gain a better understanding of the motion of the solar system and its surrounding neighborhood.

The Moon waxes in the evening sky this week, passing from the last of winter’s stars through the springtime constellations. By the end of the week she is poised to greet bright Jupiter. First Quarter occurs on June 3rd at 7:06 pm Eastern Daylight Time. Look for Luna between the Twin Stars of Gemini, Castor and Pollux, and ruddy Mars on the evening of the 30th. On the following night she lies less than three degrees north of Saturn. If you have binoculars, look between Saturn and the Moon for the scattered stars of the Beehive star cluster.

We are now approaching the shortest nights of the year. June evenings are characterized by more earthly lights. Fireflies will soon be launching themselves into their courtship flights, delighting children of all ages. The long, lazy twilights of the season last well into the evening hours, and as the month progresses the last of winter’s stars beat a hasty retreat. High overhead in the glow of twilight is one of the most prominent and isolated bright stars in the sky, the rose-tinted beacon known as Arcturus. It is the third-brightest star in the entire sky, and one of the closest of the so-called “giant” stars. It is some 300 times more luminous than the Sun, and it lies just under 37 light-years away from us. If you were born in 1969, the light you see tonight from Arcturus began its journey toward us at that time. Hypothetical Arcturians would just be learning about the Apollo 11 Moon landing about now.

Another reddish object may be found in the western sky as twilight deepens. Although he’s not as bright as Arcturus, Mars still catches the eye as he passes by the stars Castor and Pollux in Gemini. All three objects greet the crescent Moon on the evening of the 30th.

Saturn bides his time waiting for Mars to arrive in another two weeks. The ringed planet is slowly drifting eastward under the scattered stars of the Beehive star cluster. With the late ending of evening twilight you’ll have barely an hour to catch a binocular glimpse of the planet and cluster against a dark sky.

Jupiter is really putting on a show. Despite his low altitude for this year’s apparition, the giant planet has been a great target for amateur telescopes. Over the past several weeks a number of striking features have appeared in his turbulent cloud belts, including a long-lived oval that has changed from white to red in color. Now known as “Red, Jr.,” this feature alone would be worth staying up to see, but there is now a prominent red stripe that has appeared in the great South Equatorial Belt. Who knows what will happen next?

Dazzling Venus skulks in the glow of morning twilight in the hour before dawn. You’ll find her low in the east among the rising stars of the autumn sky.

The flower-like image of this star-forming region in Earth’s southern skies was imaged using a 64-megapixel Mosaic imaging camera on the National Science Foundation’s Victor M. Blanco telescope at Cerro Tololo Inter-American Observatory.

Cometary globules are isolated, relatively small clouds of gas and dust within the Milky Way. This example, called CG4, is about 1,300 light years from Earth. Its head is some 1.5 light-years in diameter, and its tail is about 8 light-years long. The dusty cloud contains enough material to make several Sun-sized stars. CG4 is located in the constellation of Puppis.

The head of the nebula is opaque, but glows because it is illuminated by light from nearby hot stars. Their energy is gradually destroying the dusty head of the globule, sweeping away the tiny particles which scatter the starlight. This particular globule shows a faint red glow from electrically charged hydrogen, and it seems about to devour an edge-on spiral galaxy (ESO 257-19) in the upper left. In reality, this galaxy is more than a hundred million light-years further away, far beyond CG4.

The image from the 4-meter telescope was taken in four filters, three of which are for blue, green and near-infrared light. The fourth is designed to isolate a specific color of red, known as hydrogen-alpha, which is produced by warm hydrogen gas.

This image shows a deep Hydrogen-alpha image of the brightest X-ray source in the sky, NGC 1275, taken by the WIYN 3.5-meter telescope at Kitt Peak National Observatory near Tucson, AZ, in 1999.

The filaments emanating from this galaxy are produced through largely unknown mechanisms, but they likely are the result of an interaction between the black hole in the center of the galaxy and the intracluster medium surrounding it. (The glowing background objects in this image are galaxies in that same galaxy cluster.)

At a distance of about 230 million light-years, this is the nearest example to Earth of such vast structures, which are seen surrounding the most massive galaxies throughout the Universe.

Galaxy Evolution Explorer engineers are working on the telescope's far-ultraviolet detector, which has not been in use since it began experiencing excessive high-voltage current draw on March 30. The team is using a technique referred to as "hi-potting," or cycling the detector on and off at progressively higher voltage, to correct the problem. About a year ago the detector experienced the same type of anomaly, and applying the hi-pot technique restored the detector to full operations. Three years after its launch, the spacecraft continues to return images of galaxies and stars obtained by its near-ultraviolet detector, which is operating normally.

These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, show Aram Chaos, 280-km-wide circular structure characterized by chaotic terrain.

The HRSC obtained these images during orbit 945 with a ground resolution of approximately 14 metres per pixel. The images show the region of Aram Chaos, at approximately 2° North and 340° East.

Aram Chaos is a 280-km-wide almost-circular structure located between the outflow channel Ares Vallis and Aureum Chaos. It is one of many regions located east of Valles Marineris and characterized by chaotic terrain.

As the name 'chaos' suggests, this terrain comprises large-scale remnant massifs, large relief masses that have been moved and weathered as a block. These are heavily eroded and dominate the circular morphology, or structure, which may have formed during an impact. As seen in the colour image, these remnant massifs range from a few kilometres to approximately ten kilometres wide and have a relative elevation of roughly 1000 metres.

The western region of the colour image is characterized by brighter material, which seems to be layered and could be the result of sedimentary deposition. Distinct layering, causing a terrace-like appearance, is also visible east of this brighter material and in the relatively flat region located in the northwest of the colour image.

Some scientists believe that the numerous chaotic regions located in the eastern part of Valles Marineris were the source of water or ice thought to have created the valleys that extend into Chryse Planitia. These regions are particularly interesting because they may yield clues to the relationship between Valles Marineris, the chaotic terrain, the valleys and the Chryse basin.

The colour scenes have been derived from the three HRSC-colour channels and the nadir channel. The perspective view has been calculated from the digital terrain model derived from the stereo channels. The anaglyph image was calculated from the nadir and one stereo channel. Image resolution has been decreased for use on the internet.

Saturn's largest moon, Titan, peaks out from under the planet's rings of ice.

This view looks toward Titan (5,150 kilometers, or 3,200 miles across) from slightly beneath the ringplane. The dark Encke gap (325 kilometers, or 200 miles wide) is visible here, as is the narrow F ring.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were taken with the Cassini spacecraft narrow-angle camera on April 28, 2006 at a distance of approximately 1.8 million kilometers (1.1 million miles) from Titan. Image scale is 11 kilometers (7 miles) per pixel on Titan.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

This picture is a composite of Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) daily global images acquired at Ls 53° during a previous Mars year. This month, Mars looks similar, as Ls 53° occurred in mid-May 2006. The picture shows the north polar region of Mars. Over the course of the month, additional faces of Mars as it appears at this time of year are being posted for MOC Picture of the Day. Ls, solar longitude, is a measure of the time of year on Mars. Mars travels 360° around the Sun in 1 Mars year. The year begins at Ls 0°, the start of northern spring and southern autumn.

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Scheduled for launch in 2007, the Gamma-ray Large Area Space Telescope (GLAST) will explore the Universe in gamma-rays, the most energetic form of light. To get ready, consider this dynamic gamma-ray sky animation – constructed from simulating the first 55 days (seen above at one frame per day) of GLAST observations of cosmic gamma-ray sources. The all-sky view is projected in an astronomical (RA-Dec) coordinate system that shows the plane of our Milky Way Galaxy as a broad U-shape, with the center of the galaxy toward the right. So what shines in this gamma-ray sky? Besides the diffuse Milky Way glow, astronomers testing their skills on the simulated data have found flaring active galaxies, pulsars, gamma-ray bursts, the flaring Sun, and of course, the gamma-ray Moon.

One electrical device which serves as a model for cosmic plasma activity is the capacitor. A capacitor is a device for accumulating and storing electric charge. It is made of two conductors separated by an insulating medium. When charge is placed on one conductor it attracts charge of the opposite polarity on the other conductor. As a result, an electric field is set up between the conductors, a reservoir of electrical energy.

In both everyday electronics and advanced plasma research the capacitor is important for its ability to rapidly store and release electrical energy. Some of the highest energy experiments in the world are performed using large rooms full of charged capacitors to produce intense discharges.

As the charge on the capacitor increases, the electric field between the conductors will increase, placing a growing stress on the insulator. At some critical point, the insulator breaks down and the capacitor "short circuits," releasing the stored electrical energy suddenly. Such breakdowns may destroy a solid insulator and with it, the capacitor.

However, if the charging rate is slow and the insulator is air or liquid, the damage may repair itself as fresh insulating material rushes in. That is a "self-repairing" capacitor. If the current is strong or the insulator weak, current will pass between the conducting plates, either steadily or in bursts. This is called a "leaky capacitor."

Power transmission lines form large-scale capacitors with the air as insulator between the conducting wires. The geometry makes the electric field strongest at the wire surface, which is where the air is likeliest to "break down" and discharge. The hissing and crackling you hear when standing under a power line is just this intermittent leakage.

Many natural systems form capacitors as well. For example, the Earth's surface and its ionosphere are two conducting layers separated by air. The surface-ionosphere capacitor is of particular interest in the study of sprites. Small "leaks" in the form of lightning can trigger much larger "leaks" (sprites, etc.) at high altitudes above them.

In the electric universe, this effect can be traced via auroral circuits, through the circuitry of the solar system, and far into interstellar space. From this viewpoint sprites and lightning are merely leakage currents trickling off the galactic power line. But clearly, the degree to which electric potential from the galaxy powers thunderstorms on Earth has yet to be investigated.